1. Field of the Invention
This invention relates to a read-out scanning exposure method and apparatus, in which an image recording medium carrying image information recorded thereon is scanned with line light beams having been radiated out from line light sources, the scanning being performed in a scanning direction intersecting with a longitudinal direction of each of the line light sources, in order for the recorded image information to be read out from the image recording medium.
2. Description of the Related Art
Image information recording and read-out systems, in which electrostatic recording materials are utilized, have heretofore been proposed. With the proposed image information recording and read-out systems, such that a radiation dose delivered to an object during a medical X-ray image recording operation may be kept small, and such that the image quality of an image and its capability of serving as an effective tool in, particularly, the efficient and accurate diagnosis of an illness may be enhanced, a photo-conductive material sensitive to X-rays, such as a selenium plate constituted of, e.g., amorphous selenium (a-Se), is employed as an electrostatic recording material. The electrostatic recording material is exposed to radiation, such as X-rays, carrying radiation image information, and latent image charges carrying the radiation image information are thereby accumulated in the electrostatic recording material. Thereafter, the electrostatic recording material is scanned with a line light beam, which has been radiated out from a line light source, and currents occurring in the electrostatic recording material are detected via a striped electrode. In this manner, the electrostatic latent image represented by the latent image charges, i.e. the radiation image information, is read out. (The image information recording and read-out systems, in which the electrostatic recording materials are utilized, are described in, for example, U.S. Pat. No. 6,268,614.)
Also, image information recording and read-out systems, in which stimulable phosphor sheets are utilized as recording media, have heretofore been proposed. With the proposed image information recording and read-out systems, a stimulable phosphor sheet, on which radiation image information has been stored, is scanned with a line light beam, which has been radiated out from a line light source and which causes the stimulable phosphor sheet to emit light in proportion to the amount of energy stored on the stimulable phosphor sheet during exposure of the stimulable phosphor sheet to radiation. Also, the light, which is emitted by the stimulable phosphor sheet when the stimulable phosphor sheet is exposed to the line light beam, is detected. In this manner, the image information, which has been stored on the stimulable phosphor sheet, is read out. As a detecting section for detecting the light emitted by the stimulable phosphor sheet, a photodiode image sensor, a charge coupled device (CCD) image sensor, or a panel-shaped or line-shaped detector, which is provided with a photo-conductive layer capable of exhibiting electrical conductivity when being exposed to the light emitted by the stimulable phosphor sheet. (The image information recording and read-out systems, in which the stimulable phosphor sheets are utilized as the recording media, are described in, for example, U.S. Laid-Open No. 20030057386.)
In the image information recording and read-out systems described above, a read-out scanning exposure apparatus, in which the scanning exposure with the line light beam is performed by mechanically moving the line light source, is utilized. However, in cases where the readout of the image information is performed by use of the read-out scanning exposure apparatus described above, it is not always possible to move the line light source quickly, and it often occurs that the read-out speed is not capable of being kept high. Therefore, there has been proposed a read-out scanning exposure apparatus, wherein a panel-shaped light irradiating section constituted of a plurality of line light sources, which are located at approximately identical pitches and in parallel with one another, is controlled such that line light beams are successively radiated out with different timing from the line light sources, and the scanning exposure with the line light beams is thereby performed. (The proposed read-out scanning exposure apparatus provided with the panel-shaped light irradiating section is described in, for example, U.S. Pat. No. 6,376,857.)
Ordinarily, the panel-shaped light irradiating section and the image recording medium should preferably be electrically isolated from each other. In the read-out scanning exposure apparatus described in U.S. Pat. No. 6,376,857, an electrical insulating layer is located between the panel-shaped light irradiating section and the image recording medium. The line light beam, which has been radiated out from the panel-shaped light irradiating section, passes through the electrical insulating layer and thereafter impinges upon the image recording medium. Therefore, in cases where a light source having a wide light distribution angle, e.g. an electroluminescent light source (an EL light source) is utilized as each of the line light sources, the line width of the line light beam impinging upon the image recording medium becomes wide.
In cases where, for example, a light converging optical system, such as a SELFOC lens array, is located between the panel-shaped light irradiating section and the image recording medium, the line light beam is capable of being converged onto the image recording medium, and the scanning exposure is capable of being performed with the line light beam having a narrow line width. However, ordinarily, the light converging optical system described above has a thickness of as large as approximately 10 mm. Therefore, in such cases, the problems occur in that the thickness of the read-out scanning exposure apparatus, which thickness is taken in the direction of the irradiation of the line light beam, becomes large, and the size of the read-out scanning exposure apparatus is not capable of being kept small.